Evolution of weed resistance to herbicides: What have we learned after 70 years?

Authors: Duke, Stephen; HEAP, IAN - National Center For Agriculture And Forestry Technologies (CENTA)

Submitted to: Book Chapter
Publication Type: Book / Chapter
Publication Acceptance Date: 3/1/2017
Publication Date: 6/1/2017
Citation: Duke, S.O., Heap, I. 2017. Evolution of weed resistance to herbicides: What have we learned after 70 years? In: Jugulam, M., editor. Biology, Physiology and Molecular Biology of Weeds. Boca Raton, FL:CRC Press. p. 63-86.

Interpretive Summary: As Darwin understood more than 150 years ago, sufficiently strong and constant selection pressure on a population of organisms over an adequate time period inevitably leads to compensatory genetic changes in that population. Synthetic pesticides have been the "perfect storm" for such a process, providing strong selection pressure on huge populations of rapidly reproducing pests.Resistance to herbicides has developed slightly slower than insecticide and fungicide resistance, but the increase in herbicide resistance has been in a rapid, linear phase since the mid-1970s. Use of glyphosate with glyphosate-resistant crops, perhaps the most effective weed control technology ever devised, is now being jeopardized by the rapid evolution of glyphosate-resistant weed species. This has occurred, even though a simple one codon mutation does not provide adequate resistance. Robust resistance glyphosate has evolved via novel mechanisms, such as gene amplification, vacuolar sequestration, or two codon changes in the target site. Now there are weed populations with resistance to more than one herbicide via multiple mechanisms. Farmers are rapidly running out of options, much like modern medicine is running out of antibiotic options because of evolved resistance in pathogens. Future technologies to cope with or overcome this problem are discussed.

Technical Abstract: As Darwin understood more than 150 years ago, sufficiently strong and constant selection pressure on a population of organisms over an adequate time period inevitably leads to compensatory genetic changes in that population. Synthetic pesticides have been the "perfect storm" for such a process, providing strong selection pressure on huge populations of rapidly reproducing pests. Resistance to herbicides has developed slightly slower than insecticide and fungicide resistance, but the increase in herbicide resistance has been in a rapid, linear phase since the mid-1970s. Use of glyphosate with glyphosate-resistant crops, perhaps the most effective weed control technology ever devised, is now being jeopardized by the rapid evolution of glyphosate-resistant weed species. This has occurred, even though a simple one codon mutation does not provide adequate resistance. Robust resistance glyphosate has evolved via novel mechanisms, such as gene amplification, vacuolar sequestration, or two codon changes in the target site. Now there are weed populations with resistance to more than one herbicide via multiple mechanisms. Farmers are rapidly running out of options, much like modern medicine is running out of antibiotic options because of evolved resistance in pathogens. Future technologies to cope with or overcome this problem are discussed.